Dengue vector — DTM&H MCQ

Correct answer: A — Aedes aegypti

The correct answer is A, Aedes aegypti. This mosquito is a daytime feeder with peak activity in the early morning and before dusk, and it breeds preferentially in small water-filled containers around human dwellings such as buckets, tyres, and cisterns, exactly matching the stem's ecology and biting pattern. It is the principal urban vector linking dengue, Zika and chikungunya, since all three arboviruses are transmitted by the same peridomestic Aedes species circulating in the same containers. Its close association with humans and their households (endophilic, anthropophilic behaviour) explains why urban outbreaks of these three arboviral infections cluster together in the same city, as seen in northern Brazil. No other listed vector transmits all three of these arboviruses simultaneously, which is the key discriminating clue in the question. Why the other options are wrong: C. Simulium damnosum: this is a blackfly that breeds in fast-flowing, well-oxygenated rivers, not stagnant water-filled containers, and it transmits Onchocerca volvulus (onchocerciasis), not dengue, Zika or chikungunya. E. Phlebotomus papatasi: this is a sandfly active mainly at dusk and night, associated with cracks in walls and rodent burrows rather than containers, and it transmits Leishmania and phleboviruses, not the arboviruses described. B. Culex tritaeniorhynchus: this mosquito is a night-biting species that breeds in rice paddies and transmits Japanese encephalitis virus, an entirely different geographic and clinical picture to this Brazilian urban outbreak. D. Anopheles gambiae: this is a night-biting African malaria vector that breeds in clean, sunlit freshwater pools, not containers, and transmits Plasmodium species, not arboviruses. Key point: Daytime biting plus container breeding plus a triad of dengue, Zika and chikungunya in an urban tropical setting is pathognomonic for Aedes aegypti.

Reference: NaTHNaC (National Travel Health Network and Centre), TravelHealthPro Dengue factsheet, UK Health Security Agency, updated 2025, https://travelhealthpro.org.uk/factsheet/13/dengue